package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate redisTemplate;

    @Autowired
    private CacheClient cacheClient ;

    private final static ExecutorService CACHE_REBUILD_EXECUTOR  = Executors.newFixedThreadPool(10);


    @Override
    public Result queryById(Long id) {

        // 缓存穿透
        // Shop shop = queryWithPassThrough(id);
        Shop shop = cacheClient.queryWithPassThrough(RedisConstants.CACHE_SHOP_KEY, id, Shop.class, this::getById, RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 互斥锁解决缓存穿透
        // Shop shop = queryWithMutex(id);


        // 逻辑过期 解决缓存击穿
        // Shop shop = queryWithLogicalExpire(id);

        if(shop == null){
            return Result.fail("店铺不存在");
        }


        return Result.ok(shop);
    }


    public Shop queryWithMutex(Long id) {

        String cacheKey = RedisConstants.CACHE_SHOP_KEY + id ;

        //1. 从redis 中查询商铺缓存
        String shopJson = redisTemplate.opsForValue().get(cacheKey);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {

            //3. 存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }

        // 判断命中的是否是空值
        if(shopJson != null){
            // 返回一个错误消息
            return null;
        }

        // 4.实现缓存重建
        // 4.1 获取互斥锁
        String lockey = RedisConstants.LOCK_SHOP_KEY + id ;
        Shop qShop = null ;
        try {
            // 4.2 判断是否 获取成功
            if (!tryLock(lockey)) {
                // 4.3 失败，则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            // 4.4 成功，根据id 查询数据库

            //4. 不存在，根据id查询数据库
            qShop = getById(id);

            //5. 不存在，返回错误
            if (qShop == null) {
                // 将空值写入redis中  2 分钟过期
                redisTemplate.opsForValue().set(cacheKey, "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);

                return null;
            }
            // 6. 存在，写入redis 中
            redisTemplate.opsForValue().set(cacheKey, JSONUtil.toJsonStr(qShop), RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);


        }catch (Exception e){
            throw new RuntimeException(e);
        }finally {
            // 7.释放互斥锁
            unLock(lockey);
        }

        return qShop;
    }


    public Shop queryWithLogicalExpire(Long id) {

        String cacheKey = RedisConstants.CACHE_SHOP_KEY + id ;

        //1. 从redis 中查询商铺缓存
        String shopJson = redisTemplate.opsForValue().get(cacheKey);

        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)) {

            //3. 存在，直接返回
            // Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return null;
        }

        // 4.命中，需要先把json 反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            // 6.未过期，直接返回店铺信息
            return shop;
        }

        // 5.2 已过期， 需要重建缓存


        // 6.缓存重建

        // 6.1 获取互斥锁
        String  lockKey = RedisConstants.LOCK_SHOP_KEY + id ;

        // 6.2 判断是否获取锁成功
        boolean isLock = tryLock(lockKey);

        if(isLock) {
            // 6.3 成功，开启独立线程，实现缓存
            CACHE_REBUILD_EXECUTOR.submit(()-> {
                try {
                    // 重建缓存
                    saveShopToRedis(id, 20L);
                }catch (Exception e ){
                    throw new RuntimeException(e) ;
                }finally {
                    // 释放锁
                    unLock(lockKey);
                }

            });
        }
        // 6.4 返回过期的商铺信息
        return shop ;
    }




    public Shop queryWithPassThrough(Long id) {

        String cacheKey = RedisConstants.CACHE_SHOP_KEY + id ;

        //1. 从redis 中查询商铺缓存
        String shopJson = redisTemplate.opsForValue().get(cacheKey);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {

            //3. 存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }

        // 判断命中的是否是空值
        if(shopJson != null){
            // 返回一个错误消息
            return null;
        }

        //4. 不存在，根据id查询数据库
        Shop qShop = getById(id);

        //5. 不存在，返回错误
        if(qShop == null){
            // 将空值写入redis中  2 分钟过期
            redisTemplate.opsForValue().set(cacheKey, "",RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);

            return null ;
        }
        // 6. 存在，写入redis 中
        redisTemplate.opsForValue().set(cacheKey, JSONUtil.toJsonStr(qShop),RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

        return qShop;
    }


    public Result queryById2(Long id) {

        String cacheKey = RedisConstants.CACHE_SHOP_KEY + id ;

        //1. 从redis 中查询商铺缓存
        String shopJson = redisTemplate.opsForValue().get(cacheKey);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)) {

            //3. 存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return Result.ok(shop);
        }

        // 判断命中的是否是空值
        if(shopJson != null){
            // 返回一个错误消息
            return Result.fail("店铺信息不存在");
        }

        //4. 不存在，根据id查询数据库
        Shop qShop = getById(id);

        //5. 不存在，返回错误
        if(qShop == null){
            // 将空值写入redis中  2 分钟过期
            redisTemplate.opsForValue().set(cacheKey, "",RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);

            return Result.fail("店铺不存在");
        }
        // 6. 存在，写入redis 中
        redisTemplate.opsForValue().set(cacheKey, JSONUtil.toJsonStr(qShop),RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);

        return Result.ok(qShop);
    }




    /**
     *  加锁逻辑
     *
     * @param key
     * @return
     */
    public boolean tryLock(String key ){

        Boolean aBoolean = redisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);

        return BooleanUtil.isTrue(aBoolean);
    }


    public void unLock(String key ){
        redisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {

        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺id不能为空");
        }

        // 1. 更新数据库
        updateById(shop);

        // 2. 删除缓存
        redisTemplate.delete(RedisConstants.CACHE_SHOP_KEY+id);


        return Result.ok();
    }


    public void saveShopToRedis(Long id , Long expireSeconds){

        // 1. 查询店铺数据
        Shop shop = getById(id);
        // 2. 封装逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        // 3. 写入redis 缓存
        redisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY+id, JSONUtil.toJsonStr(redisData));

    }














































}
